Control circuits for fire prevention apparatus



J1me- 1932- T. T. ALLEN ET'AL. 1,862,342

,ON'I'R OL CIRCUITS FOR FIRE PREVENTION APPARATUS Filed July 18, 1929 2 Sheets-Sheet l 2 fi H 58 f WITNESS: INVENTORS ThnmasTwafide] Allen I C Ifihn Francis Aflams- BY .1 W M M 5 (7 ATTORNEY June 7, 1932. T. T. ALLEN ET AL CONTROL CIRCUITS FOR FIRE PREVENTION APPARATUS 2 Sheets-Sheet 2 Filed July 18, 1929 I n5 1 E 5 m m T d I T .VMHY R mmmB 1% r 7 mm AHU I H V Patented June 7, 1932 UNITED STATES PATENT OFFICE.

THOMAS TWADDEL ALLEN AND JOHN FRANCIS ADAMS, OF PHILADELPHIA, PENN SYL- VANIA, ASSIGNORS TO SENIRY SAFETY CONTROL CORPORATION, 03 PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF DELAWARE CONTROL CIRCUITS FOR FIRE PREVENTION APPARATUS Application filed July 18,

This invention relates to the electric circuits for fire prevention apparatus used in connection with motion picture projecting machines and particularly to the novel hook- 7 up providing effective operation of the safety devices which take care of every condition which might tend to cause fire.

The object of this invention is to provide a series or net work of circuits which include means for operating the main safety unit in 0rd er to automatically control the mechanism of said unit so as to prevent fire in case there is, for any reason, faulty operation of the machine.

According to the invention, the control circuits are designed to include fire prevention apparatus in motion picture machines which have a film feeding mechanism and a motor for operating the same. The control unit includes an electro-magnet, a motor switch, a dowser mounted on a shaft, a cam on said shaft for closing the motor switch, a control plate for the dowser positioned by the energization or non-energization of the electromagnet, and means on the shaft operating in conjunction with the control plate for holding the dowser in its raised position during the normal operation of the machine, for releasing it upon faulty operation of the machine and for preventing its being raised out of light obstruction position until the film is moving with required speed across the aperture of the projecting machine.

The invention contemplates in connection with the said control unit, switches which engage the film and which are held closed by the normal advancement of the film in the machine, and which said switches are in series with the magnet circuit, a centrifugal switch whose arms are in series with the magnet and film switches during normal operation of the machine and which, when the speed falls below a predetermined rate, closes to short-circuit the electro-magnet through a protective resistance, there-by releasing the control plate and permitting the dowser to fall, thereby cutting off the rays of light from the film.

The drawings illustrate an embodiment of the invention and the views therein are as follows:

1929. Serial No. 379,091.

Figure 1 illustrates the hook-up for the several apparatuses used in operating the control unit and with said parts shown in more or less diagrammatic arrangement.

Figure 2 is a front elevation of the control unit with the front of the casing removed, and with the dowser broken away,

Figure 3 is a vertical section of the centrifugal switch, and

Figure 4 is a vertical section of same, and the line 4si in Figure 3 illustrates the point at which same is taken.

T he control unit which is illustrated in the drawings is the same as that shown and described in a patent of the applicants herein and one 5. Struthers Dunn, granted August 20, 1929, No. 1,725,556, and its main elements comprise a casing 1 having a shaft 2, which extends through the casing and on which is fastened the arm 3 of the dowser i.

The casing is also provided with a motor switch 6 which is opened and closed by means of the cam 7 fastened securely to the shaft 2 and operated by the opening and closing of the dowser.

The shaft is also provided with a cam S which cooperates with a control plate 9 in the casing and which is engaged by said plate to prevent the raising of the dowser beyond a certain fixed limit when a magnet 11 in said casing is deenergized, and when the magnet is energized, this control plate not only permits the raising of the dowser to its open position, but holds the same in said position.

The position of the control plate is regulated by the magnet keeper 12 which is adapted to be urged away from the magnet by the spring 13.

When the magnet 11 is deenergized, the dowser arm may be moved sufficiently far to cause the cam 7 to close the motor switch 6, but that movement does not move the dowser sufiicient to uncover the opening in the light cone on which the foot of the control unit is mounted.

The film switches 14 are of the conventional type and are controlled by an arm 16 having a roller 17 which engages the film, while the other end of the arm is provided with a cam 18, the slight turning of which disengages the contacts 19 and 21 so as to open the electric circuit in which the switches are included.

The centrifugal switch 22 may be identical with the switch shown and described in our Patent No. 1,809,816 granted June 16, 1931 and its operating parts consist of the pivoted arms 23 and 24 which contact with rings and 26 respectively when the iilm operating mechanism is running at a speed less than a predetermined rate and which, when the predetermined rate of speed has been reached, are thrown out centrifugally so as to break the circuit between the same. This switch is operated from one of the rotating parts of the projector through the pinion on the shaft 53. The speed at which contact is broken between the arms 23 and 24, and their respective rings 26 and 2G, is governed by springs 54 as regulated by the eccentrics WVhen'the film feeding mechanism attains a predetermined speed, the magnet 11 will be energized through the operation of the centrifugal switch 22 so that the keeper 1.2 will be drawn toward said magnet and held thereby. The spring 56 (see Fig. 2) will swing the control plate 9 inwardly, thereby pulling a lug on said plate out of the path of a finger on the latch 58 so that the dowser may then be manually swung into open position. The cam 8 by that movement will have been rotated and its face 59 will have passed a plate 60 on the bottom of plate 9 so that the spring 56 will draw the control plate 9 inwardly where the head of the set screw 61 will rest against the keeper 12, and the cam face 59 will engage the end of the plate 60 thereby locking the dowser in its raised position so that the rays of light will pass through the cone.

The relay box 27 has a relay coil 28 and an arm 29 for bridging the terminals 31 and 32 when the coil is energized. The box is also provided with a protective resistance 33 while at the other side of the relay is a strap 34 which, for the purpose of this invention, may merely be considered as a conductor.

The apparatus is wired as follows:

WVires A and B extend from a line and are fastened to suitable terminals on the relay box 27. The wire A extends to one side of the relay coil 28 and from thence a wire 36 extends to one end of the bus bar 34 and its other end connects a wire 37 which extends to the upper contact 38 of the switch 6, while the lower contact 39 of this switch is con nected by a wire 41 which leads to the arm 23 of the centrifugal switch 22. A wire 42 extends from this same arm 23 back to the line wire B.

When the switch 6 is closed, the coil 28 thereby becomes energized and its contact arm 29 will be drawn downward to bridge the contacts 31 and 32', thereby closing the motor circuitwhich extends from the wire A through the wire 43, contact 29, the wire 44 leading from the contact 32, the wire 46 leading from one side of the protective resistance 33 to one side of the motor M, while its other side is connected by a wire 47 directly to the line wire B.

The wire 41 is connected by a wire 48 to one side of the electro-magnet coil 11 and the other side of this coil is connected by a wire 49 which leads to the contact arm 24 of the centrifugal switch 22. A wire 51 also connects this arm 24 and includes in its circuits the film switches 14 and terminates at one side of the protective resistance 33 where it is connected to a binding post 52.

In the operation of the machine from a position of rest, the dowser arm 3 is first moved slightly to the right causing the dowser to move slightly in a direction shown by the arrow P. This movement will rotate the shaft 2 which in turn rotates the cam 7 which closes the motor switch 6. Current will then flow from the wire B through the wire 42, the centrifugal switch arm 23, wire 41, the motor switch 6, the wire 37, the bus bar 34, the wire 36, the coil 28, back to the line wire A. The closing of this circuit will energize the coil 28 which will draw the contact arm 29 downward so to bridge the contacts 31 and 32, thereby closing the motor circuit through the wire B, motor M, wire 46, wire 44, contact arm 29, wire 43, back to the line wire A.

Until the motor attains a certain predetermined speed so as to move the film F with certain rapidity across the aperture of the machine, the contact arms 23 and 24 of the centrifugal switch 22 will continue to make contact with the contact ring or rings 26, thereby maintaining a circuit as follows From the line wire B through the wire 42 to the contact arm of the centrifugal switch 22, thence through the contact ring or rings 26 to the contact arm 24, thence through the wire 51 through the film switches 14 down to the terminal 52 of the protective resistance thence through the wire 44 extending from the other terminal 53 of the protective resistance to the contact 32 of the relay, thence across the contact arm 29 to the contact 31, and thence through the wire 43 to the line wire A.

During the flow of current through the last mentioned circuit, the magnet will be dcenergized and the control plate 9 through its connection with the cam 8 on the shaft 2 will prevent the dowser from being manually raised beyond its open position and will thereby prevent the film from being exposed to the intense rays of light from the lamphouse (not shown) while the machine is building up sufiicient speed to carry the film across the aperture at such a rate that the rays of light will not ignite the same.

WVhen, however, the required or predetermined speed has been attained, the contact arms 23 and 24 of the centrifugal switch 22 will be thrown out centrifugally, thereby breaking their contact or contacts with the contact ring or rings 26 so as to open the circuit across the same and to re-arrange the circuit so that it will extend from the line wire B through the wire 42, the wire 41, wire 48 to electro-magnet 11, wire 49 from the other side of the electro-magnet to the contact 24:, thence through the wire 51 including the film switches and down to the protective resistance 33, and thence through the relay to the line wire A.

It will be readily understood that this circuit will be instantly broken by the operation of either of the switches 14 which will deenergize the magnet 11, thereby operating the control plate 9 to release the dowser at which, in falling, will rotate the shaft 2, thereby rotating the cam 7 to open the motor switch 6.

If, for any reason, such as decrease in the impressed E. M. R, the breaking of a motor belt, the breaking of a brush, or other occurrence which causes a decrease in the speed of the film feeding mechanism, the speed of the centrifugal switch 22 will be likewise decreased and the contact arms 28 and 24: thereof will then reenergize the contact ring or rings 26, short-circuiting the electro-magnet 11 and providing exactly the same circuit through the protective resistance 83 which was maintained during the starting of the machine and with the centrifugal switch closed.

Of course, the mechanism comprising the safety unit, switches and relay are not intended to be covered by the claims hereof, but only such portions thereof that are neces sary for the control circuits disclosed herein; consequently, the mechanism and circuits illustrated may be changed in various ways without'departing from the invention herein disclosed and hereafter claimed.

The invention is hereby claimed as follows 1. Control circuits for fire prevention apparatus for a motion picture machine having a film feeding mechanism and'a motor for operating the same, a control unit including an electro-magnet, a motor switch, a dowser mounted on a shaft, a cam on said shaft for closing the motor switch, and a control plate for the dowser, switches engaging the film and held closed thereby during the normal advancement of the film in the machine, a centrifugal switch, a relay, and a protective resistance, a circuit including the coil of the relay and the motor switch closed by the cam upon a slight upward manual movement of the dowser, a motor circuit closed by the energization of said relay coil, a circuit including the film switches, the motor switch and the centrifugal switch in series and which includes the magnet when the machine is operating at a predetermined speed, said centrifugal switch being adapted to short-circuit the magnet through said protective resistance until said machine has attained its required speed, thereby positioning the control plate to prevent the raising of the dowser to open position.

2. Control circuits for fire prevention apparatus for a motion picture machine having a film feeding mechanism and a motor for operating the same, a control unit including an electro-magnet, a motor switch, a dowser mounted on a shaft, a cam on said shaft for closing the motor switch, and a control plate for the dowser, switches engaging the film and held closed thereby during the normal advancement of the film in the machine, a centrifugal switch, a relay, and a protective resistance, a circuit including the coil of the relay and the motor switch closed by the cam upon a slight upward movement of the dowser, a motor circuit closed by the energization of said relay coil, a circuit leading from the motor switch through the closed centrifugal switch, said protective resistance, and the film switches when the machine has not attained its required speed, and which when the said speed is attained opens the centrifugal switch to include the motor switch, electro-magnet and film switches in series, the magnet thereby moving the control plate and unlocking the dowser whereby it may be raised to open position.

3. Control circuits for fire prevention apparatus for a motion picture machine having a film feeding mechanism and a motor for operating the same, a control unit including an electro-magnet, a motor switch, a dowser mounted on a shaft, a cam on said shaft for closing the motor switch, and a control plate for locking the dowser when the magnet is deenergized to prevent the dowser from being raised to open position but permitting its manual movement to close the motor switch through the cam, switches engaging the film and held closed thereby during the normal advancement of the film in the machine, a centrifugal switch, a relay, and a protective resistance, a circuit including the film switches, the motor switch and the centrifugal switch in series and which includes the magnet when the machine is operating at a predetermined speed, said centrifugal switch being adapted to short-circuit the magnet through said protective resistance until said machine has attained its required speed, the control plate thereby preventing the raising of the dowser to open position.

4. Control circuits for fire prevention apparatus for a motion picture machine having a film feeding mechanism and a motor for operating the same, a control unit including an electro-magnet, a motor switch, a dowser mounted on a shaft, a cam on said shaft for closing the motor switch, and a control plate for the dowser, switches engaging the film and held closed thereby during the normal 1 advancement of the film in the machine, a

centrifugal switch, a relay, and a protective resistance, a circuit including the coil of the relay and the motor switch closed by the cam upon a slight upward movement of the dowser, a motor circuit closed by the energization. of said relay coil, a circuit including the film switches, the motor switch and the centrifugal switch in series and which includes the magnet when the machine is operating at a predeterminedspeed, said centrifugal switch being adapted to short-circuit the magnet through said protective resistance until said machine has attained its required speed, the control plate locking the dowser to prevent the raising'of the same to open position, said last circuit adapted to be broken by the faulty feeding of the film whereby a film switch is opened which deenergizes the magnet, releases the dowser which in falling rotates the cam to open the motor circuit.

In testimony whereof I have signed my name to this specification.

THOMAS TWADDEL ALLEN. In testimony whereof I have signed my name to this specification.

JOHN FRANCIS ADAMS. 

